@article{DAN_1957_116_5_a5,
     author = {A. I. Mal'tsev},
     title = {On classes of models which possess the operation of generation},
     journal = {Doklady Akademii Nauk},
     pages = {738--741},
     publisher = {mathdoc},
     volume = {116},
     number = {5},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_116_5_a5/}
}